Support Named Graphs

[twalmsley]

At present MC works with the default graph in each dataset wrapped by MagmaCoreService, but it is likely to be useful if MC supported named graphs as well. This would allow related but independent datasets to be stored separately in the same dataset.

Here is what ChatGPT says about the purpose and uses of named graphs:

Named graphs in the context of RDF (Resource Description Framework) triplestores serve several important purposes, enhancing the flexibility and utility of RDF stores for storing and querying semantic web data. RDF is a standard model for data interchange on the web, and it represents information as triples, consisting of a subject, predicate, and object. However, RDF by itself doesn't provide a native way to group triples or to store metadata about groups of triples. This is where named graphs come into play. The purposes of named graphs include:

1. Graph Partitioning: Named graphs allow for the logical partitioning of data within a single RDF store. This means that triples related to different datasets, domains, or contexts can be stored in separate graphs, making data management more organized and efficient.

2. Provenance Tracking: They enable tracking the provenance of data. By associating a set of triples with a named graph, it's possible to record where the data came from, who created it, and when it was added to the store. This is crucial for applications where the source and reliability of information are important.

3. Access Control: Named graphs can facilitate more granular access control mechanisms. Permissions can be set at the graph level, allowing different users or applications to access only specific subsets of data within the triplestore.

4. Versioning and Changesets: They can be used to manage different versions of the same data or to record changes over time. Each version or changeset can be stored in a separate named graph, enabling historical queries and the tracking of data evolution.

5. Inference and Reasoning Scopes: In semantic web applications, inference and reasoning are often applied to derive new knowledge from existing data. Named graphs can define the scope of reasoning, limiting it to specific datasets, which can improve performance and ensure that inferred knowledge is contextually relevant.

6. Querying Flexibility: Named graphs add flexibility to querying. SPARQL, the RDF query language, supports querying over specific named graphs or combinations of graphs, allowing for more precise and context-aware queries. This means that users can target their queries to specific datasets or views of the data.

7. Data Integration: In scenarios involving data integration from multiple sources, named graphs can represent each source's data separately. This segregation makes it easier to handle discrepancies, conflicts, or duplications across datasets.

Named graphs are identified by URIs (Uniform Resource Identifiers), allowing them to be precisely referenced and manipulated. The concept of named graphs significantly extends the power and applicability of RDF triplestores in managing complex and diverse semantic web data.